The Out-of-MUX framework is a technology that simultaneously reads a digital stream recorded on a read-only recording medium, such as a BD-ROM, and a digital stream recorded in a local storage, which is a rewritable recording medium, supplies them to a decoder, and then plays back them synchronously.
Here, assume that the digital stream recorded on a BD-ROM is a main portion of a movie while the digital stream recorded in a local storage is a commentary of the director of the movie. In this case, by realizing the above-mentioned Out-of-MUX framework, the main portion of the movie on the BD-ROM and the commentary can be played back together, which thereby improves and expands content on the BD-ROM.
The prior art regarding read-only recording media includes the following patent application.    <Patent Reference 1> Japanese Laid-Open Patent Application No. H8-83478